1.   The fires caused widespread smogs, limiting visibility and forcing the closure of airports and shipping lanes.

2.   Any plant that meets the other criteria and can be identified as contributing to any pollution that limits visibility in any national park is covered by the rules.

3.   Asher said smoke from the fires, which has limited visibility in the area, would have caused a crowd control problem.

4.   Blowing dust will limit visibility in some areas.

5.   A season of heavy fog that can limit visibility to just a few feet is fast approaching, Charles said.

6.   Churning clouds of particles often limited the visibility of the scientific observers to about a yard or less.

7.   Farther north, fog will limit visibility in much of interior Washington.

8.   Furthermore, at the upper altitudes snow will being falling in six weeks or less, limiting visibility for Russian aircraft and artillery and obstructing mountain passes.

9.   Francis said the work kicked up sand that limited visibility and slowed recovery.